Automatic network switching systems in the past, for example, have been adapted to use wireless terminals supporting two kinds of access networks of a wireless LAN and a PHS and properly switch connection between the access networks in accordance with the signal levels and in the order of priority in consideration of the service fees (Patent Document 1).
In addition, in order to expand the service area of a wireless LAN, there have further been proposed a system that includes a wireless relay device between wireless LAN terminals and a wireless LAN access point and a system that causes another wireless LAN terminal to function as a relay device (Patent Documents 2 and 3).
There has been studied migration management for implementing seamless handoff when wireless terminals move between access networks with different wireless interfaces.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2004-179958    Patent Document 2: Japanese Unexamined Patent Application Publication No. 2004-007411    Patent Document 3: Japanese Unexamined Patent Application Publication No. 2003-249937